1. Technical Field. This invention relates generally to the processing of miniature electronic components such as ceramic chip capacitors and resistors, and particularly to a device useful in handling these components during the process of applying a conductive coating to the component ends.
2. Background Information. The tiny size of many chip capacitors and resistors complicates batch processing. Fabricated in right rectangular shapes having dimensions on the order of 0.140".times.0.120".times.0.040", these difficult to handle components require appropriate equipment and precision handling techniques if processing is to be performed economically. End coating the component is of particular concern.
End coating prepares the component ends so that they can be soldered for electrical connection in a circuit. Typically accomplished by dipping the component ends in an electrically conductive coating material, end coating results in a quantity of the conductive material adhering to the component end as an electrical connection to the element within. But the small component size greatly complicates this process without proper equipment.
U.S. Pat. Nos. 4,381,321, 4,393,808, and 4,526,129 describe systems that may be used for this purpose, and they are incorporated herein by reference for the details of the existing end-coating equipment and techniques they described.
According to these patents, vacuum assisted vibration equipment loads a component into each one of a regular array of openings in a rectangular loading plate. A bank of pins in a press then transfers the components from the loading plate to corresponding holes in a part handling or carrier plate. The carrier plate holes are slightly undersized to frictionally retain the components, and with the component ends protruding slightly from these holes, the carrier plate is passed by a coating mechanism which transfers conductive material to the component ends.
Thus, lining up the components in a carrier plate enables end coating in significant batches despite the many complications attending tiny component size. But effective as they are, existing carrier plates suffer from certain drawbacks.
Existing carrier plates are typically fabricated from a rectangular aluminum plate having a size on the order of 7" by 11" by 11/32" thick. A regular array of holes is predrilled in the plate, a pattern of 51 holes by 83 holes for a total of 4,233 holes being typical. The hole size, and consequently the array size, may differ according to the size of the components to be handled.
Once the holes have been formed, the plate is coated with a compliant material that fills the holes. An elastomer coating such as silicon rubber resin is often employed for this purpose.
After the compliant material cures, a new set of smaller holes, on the order of 0.046" to 0.110" in diameter (depending on component size) is drilled in line with the original holes, so that a coated plate with an array of lined holes results. These resulting holes, or receptor holes, are slightly smaller than the components to be handled, so that the components can be gently forced into the receptor holes and retained in place for end coating.
Thus, existing carrier plates involve a multi-step fabrication process that is time consuming and correspondingly expensive to accomplish. In addition, special procedures must be employed to apply the compliant material to the plate, followed by a second precise drilling operation to complete the receptor holes. Consequently, it is desirable to have a new and improved carrier plate design that is more convenient and less expensive to fabricate.
Once fabricated, existing carrier plates experience abrasive wear and temperature degradation during use. This is aggravated by the large expanse of compliant material covering the surface of the plate where it is exposed to damage. Consequently, it is desirable to have a carrier plate that has less compliant material exposed, to thereby inhibit wear and degradation.
When abrasive wear and temperature degradation reaches a point necessitating repair or replacement, existing carrier plates exhibit further drawbacks. Though less expensive to repair than replace, repair requires dissolving and scrapping and otherwise removing the compliant material from the aluminum plate. Then fresh material must be applied, cured, and redrilled. This is time consuming and expensive to accomplish, and the damaged carrier plate must be taken out of service and shipped to repair facilities having the means for performing these operations. Consequently it is desirable to have a carrier plate that can be quickly and easily repaired--one enabling replacement of the compliant material by a user with a few simple operations.
Thus, it is desirable to have a new and improved carrier plate that alleviates the above mentioned concerns, while being compatible with other existing component handling equipment.